Optical signature of structural relaxation in glassy As10Se90

Temperature dependence of optical transmission in the fundamental optical absorption edge region is studied through the glass transition interval for the typical representative of fragile As-Se glasses. Near-linear temperature dependence of the optical characteristics is observed for the non-aged As10Se90 glass through the whole investigated range of temperatures, while a well-expressed non-linear peculiarity in the vicinity of glass transition is recorded for the 1 year and 20 years aged samples. It is associated with restoration of the optical properties of supercooled liquid during glass-to-supercooled liquid transition and is directly observed in the temperature range where the endothermic peak in DSC curves is observed. It is shown that long-term physical ageing at normal conditions results in a bleaching effect. Observed phenomenon is discussed in terms of the microstructural model of natural physical ageing developed recently.